In fluidized bed combustion chambers removable nozzle units for fuel and combustion air typically are used to facilitate service. The nozzles operate in a high temperature, high stress environment and there is a risk of clogging of the fuel pipe, for example through carbonization of the fuel. Because the nozzle units for air and fuel are removable and the bushings therefor may be sealed during the removal, the operation of the combustion chamber may continue during the removal of an air-fuel nozzle for inspection and cleaning.